1. Field of the Invention
The invention relates to a method for taking a sample which is representative of the fluid, in particular of the gas, in a well at a given depth, and a sampling device for carrying out this method.
2. Description of the Related Art
There is already known a method which is based upon the use of a sampling device which comprises a bottle closed at one end and containing a piston. The bottle contains hydraulic oil separated from the fluid of the well by the piston. According to this method, the sampler is lowered to a desired depth in the well. To take a sample, the bottle is put in communication with a chamber provided inside the sampler and which is at atmospheric pressure. The hydraulic oil then flows from the bottle into the chamber through a pressure reducing valve. The piston moves back and slowly draws in the fluid from the well. The bottle closes when the piston reaches the bottom of the bottle.
This known method makes it possible to take a sample without varying its pressure or its temperature. It does not, however, guarantee the chemical integrity of the sample of the fluid of the well at the sampling depth. Indeed, the bottle is open at one end and may include a small amount of grease. Moreover, a film of hydraulic oil may remain on the bottle by the piston during the sampling.
The object of the invention is to provide a method and a sampling device which do not suffer from the problems discussed above.